1. Field of the Invention
The present invention is a device for harvesting ears of fresh sweet corn.
2. Background of the Invention
Fresh market sweet corn (i.e., fresh corn distributed in its husk) can command premium market prices if it has "hand-picked" appearance and quality. These desirable characteristics include a long shank, intact outer flag leaves and no husk damage. However, it can be relatively expensive and inefficient to pick fresh market sweet corn by hand. Mechanical headers or harvesters capable of harvesting fresh market sweet corn to hand-picked quality standards are therefore often used for this purpose. Harvesters of this type are commercially available from a number of manufacturers, including Pixall of Clear Lake, Wis.
The Pixall fresh market sweet corn harvester includes a mounting frame pivotally mounted to the front of a drive chassis, and a harvesting unit for each row of corn to be harvested. Hydraulic cylinders extending between the mounting frame and chassis are actuated to raise and lower the harvester. Each harvesting unit includes a cutter for cutting lower portions of the corns stalks at a cut height above the ground, a stripping mechanism for removing ears of corn from the cut stalks, and a gathering mechanism for engaging upper portions of the cut corn stalks at a gripping height and pulling the stalks through the stripping mechanism. The distance between the cutters and the stripping mechanisms is known as the stripping window height, and was set by spacers which were mounted to the harvester frame.
A gauge wheel is pivotally mounted to the leading edge of the harvester by a linkage, and can be raised and lowered by a hydraulic cylinder. The gauge wheel hydraulic cylinder and the mounting frame hydraulic cylinders are coupled to a header height hydraulic circuit by a float block which controls the distribution of hydraulic fluid between the cylinders in such a manner that most of the weight of the harvester is supported by the mounting frame hydraulic cylinders. When the header height hydraulic circuit is operated in a height adjustment mode, the mounting frame hydraulic cylinders and the gauge wheel hydraulic cylinder are actuated to raise and lower the harvester with respect to the chassis and ground, and thereby adjust the cut height of the harvester. When the header height hydraulic circuit is operated in a floating mode, the gauge wheel effectively functions as a ground height sensor, causing the hydraulic circuit to distribute fluid between the mounting frame cylinders and the gauge wheel cylinder in such a manner as to maintain the cutters at a constant cut height as the contour of the ground changes.
Fresh market sweet corn harvesters of the type described above generally operate most efficiently and provide the highest quality corn when set for a relatively high cut height and when the gathering unit engages the cut corn stalks relatively close to the ear. However, various varieties of sweet corn have differing plant characteristics. By way of example, the plants can have different heights, and the heights at which the ears tend to grow on the plants will vary between varieties. Furthermore, under different growing conditions the plant characteristics of any given variety can vary from field-to-field, and even within the same field. Given this range of variability in plant characteristics, it can be difficult to set and maintain the harvester at optimal conditions for high efficiency and high quality harvesting operations.
There is, therefore, a continuing need for improved fresh market sweet corn harvesters. In particular, there is a need for a harvester that can efficiently harvest different varieties of corn grown in varying field conditions. The harvester should be relatively convenient to operate. To be commercially viable, the harvester must also provide "hand-picked" quality.